some more (`refute`) mini-test compatibility
assert_not_includes/refute_includes alias for assert_not_include
add assert_not_instance_of and align assert_instance_of's failure msg 
(with assert_kind_of)
adding assert_not_kind_of
added assert_not_operator (with minitest refute compatibility)
Merge pull request #57 from kares/master

more not asserts (+ flutes)

Patch by Karol Bucek. Thanks!!!